JPH038012B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium with excellent magnetic and mechanical properties. General-purpose magnetic tape is made by dispersing acicular magnetic particles with a long axis of 1 μm or less in a binder solution with appropriate additives (dispersants, lubricants, antistatic agents, etc.) to create a magnetic paint, which is then coated with polyethylene terephthalate. It is made by coating on film. Magnetic recording media are required to have high magnetic recording density and high reproduction output, and for this purpose, it is necessary to highly fill and highly align magnetic particles with high coercive force. In order to achieve high filling and high orientation, the magnetic particles must be dispersed down to the primary particles. The dispersion of magnetic particles is greatly influenced by the binder, and no matter how efficient a dispersion machine is used, if the binder's dispersibility is low, the magnetic particles will not be dispersed in the paint. Furthermore, magnetic particles with high coercive force have been developed, but as the coercive force increases, the magnetic particles become more difficult to disperse. Traditionally, binders for magnetic paints include vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinylidene chloride copolymer, thermoplastic polyurethane resin, thermosetting polyurethane resin, and polyester resin. , acrylonitrile-butadiene copolymer, nitrocellulose, cellulose acetate-butyrate, epoxy resin or acrylic resin, etc. have been used, but for applications that require high performance such as video tape and computer tape, In particular, the current situation is that it cannot be said to have sufficient magnetic properties. It is also known to use a surfactant as a dispersant, but the presence of a low molecular weight surfactant in the magnetic coating has the drawback of deterioration of physical properties and changes over time. A magnetic tape must not only have excellent magnetic properties but also excellent mechanical properties such as abrasion resistance, runnability, flexibility, and adhesion to a support. Magnetic tape that uses polyester resin or polyurethane resin as a binder has excellent mechanical properties and is a useful material as a magnetic tape binder.
23500, 45−24902, 49−48126, 48−31611, 48−
31610, 42-15432, 51-6522). In view of the above circumstances, the inventors of the present invention have conducted extensive studies with the aim of improving the dispersibility of magnetic particles while retaining the mechanical properties of polyester resins and polyurethane resins. The present invention has been achieved by discovering that the above object can be achieved by using the following. That is, the present invention provides a magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, and a phosphorus compound having an ester-forming functional group is reacted as the binder. A magnetic recording medium characterized by using polyester resin and/or polyurethane resin. In the present invention, by using a polyester resin or polyurethane resin reacted with a phosphorus compound having an ester-forming functional group as a binder, the mechanical properties of the polyester resin or polyurethane resin are maintained, and the magnetic particles are A magnetic recording medium with improved dispersibility can be obtained. Examples of the phosphorus compound having an ester-forming functional group used in the present invention include a phosphorus compound represented by the following formula (). (In the formula, R ₁ is a monovalent ester-forming functional group. _{R 2} and R ₃ are the same or different groups,
It is selected from the group consisting of a monovalent hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, and a monovalent ester-forming functional group. A represents a divalent or trivalent organic residue. Further, n ₁ is 1 or 2, and n ₂ and n ₃ each represent an integer of 0 to 4. ) Phosphorus compounds other than the phosphorus compounds used in the present invention, such as phosphoric acid esters such as triphenyl phosphate and phosphonic acids such as benzenephosphonic acid derivatives, can improve the dispersibility of magnetic particles compared to conventional binders. This may cause deactivation of the catalyst during the production of polyester resin, deterioration of resin properties due to formation of ether bonds, or gelation of the polymer. Furthermore, the resulting resin has poor durability and is less suitable as a binder for magnetic recording media. The carboxylic acid component of the polyester resin used in the present invention includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid, p-oxybenzoic acid,
Aromatic oxycarboxylic acids such as p-(hydroxyethoxy)benzoic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, tri- and Examples include tetracarboxylic acid. Particularly preferred are terephthalic acid, isophthalic acid, adipic acid, and sebacic acid. In addition, the glycol components of the polyester resin include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-
hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol,
2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, ethylene oxide adduct and propylene oxide adduct of bisphenol A, ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A , polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. Also trimethylolethane,
Tri- and tetraols such as trimethylolpropane, glycerin, and pentaerythritol may be used in combination. The polyester resin of the present invention has the above carboxylic acid,
It is obtained by reacting a phosphorus-based compound having an ester-forming functional group with glycol and, if necessary, a trihydric or higher polyhydric alcohol. The polyester resin used in the present invention preferably has a reduced viscosity of 0.4 dl/g or more, particularly 0.6 to 1.0 dl/g. The polyurethane resin of the present invention is obtained by reacting a polyhydroxy compound with a polyisocyanate, and part or all of the polyhydroxy compound is a phosphorus compound or a reaction product thereof. The phosphorus compound used in the polyurethane resin is one in which R ₁ in the above formula () is a functional group containing a hydroxyl group, and the reaction product of the phosphorus compound is particularly the phosphorus compound used in the present invention with a molecular weight of 1,000 to 10,000. A polyester resin containing is desirable. It may also be used in combination with polyhydroxy compounds that do not contain phosphorus, such as ordinary polyester polyols, polyether polyols, acrylic polyols, castor oil derivatives, tall oil derivatives, and other hydrous acid group compounds. Further, when producing the polyurethane resin of the present invention, it is preferable to use one or more types of known compounds such as glycols, diamines, and amino alcohols as chain extenders, and among them, glycols are particularly preferable. Examples of the polyisocyanate used in the polyurethane resin of the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, and hexamethylene diisocyanate. , tetramethylene diisocyanate, 3,3'-
Dimethoxy-4,4'-biphenylene diisocyanate, 2,4-naphthalene diisocyanate,
3,3'-dimethyl-4,4'-biphenylene diisocyanate, 4,4'-diphenylene diisocyanate, 4,4'-diisocyanate-diphenyl ether, 1,5-naphthalene diisocyanate,
p-xylylene diisocyanate, m-xylylene diisocyanate, 1,3-diisocyanate methylcyclohexane, 1,4-diisocyanate methylcyclohexane, 4,4'-diisocyanate dicyclohexane, 4,4'-diisocyanate dicyclohexylmethane, isophorone diisocyanate, etc. However, if necessary, 2, 4,
Small amounts of 4'-triisocyanate-diphenyl, benzene triisocyanate, etc. can also be used. Polyurethane resin can be obtained by reacting a polyhydroxy compound and a polyisocyanate in a solvent or in the absence of a solvent using a known method, but the desirable blending ratio is
NCO group/OH group of polyhydroxy compound = 0.5~
It is 2/1. The molecular weight of the resulting polyurethane resin is preferably 8,000 to 100,000. Polyester resin used in the present invention,
Phosphorous compounds that characterize polyurethane resins include those represented by the above formula (). Specific examples include the following. In the present invention, it is appropriate to use the compound represented by the general formula () in a polyester resin or polyurethane resin so that the amount of phosphorus atoms is 500 to 40,000 ppm, and if the amount is less than the above range, the dispersibility for magnetic particles will decrease. On the other hand, if the amount exceeds the above range, the physical properties deteriorate, particularly the adhesion to polyester films. In the present invention, in addition to the polyester resin and polyurethane resin, other compatible resins are added for the purpose of adjusting the flexibility of the magnetic tape, improving heat resistance, etc., and/or the polyester resin and the polyurethane resin are added. It is desirable to mix a compound that reacts with the resin and crosslinks it. Examples of resins compatible with the polyester resin and polyurethane resin used in the present invention include vinyl chloride resins, polyester resins, cellulose resins, and the like. On the other hand, examples of compounds that crosslink with polyester resins and polyurethane resins include epoxy resins, isocyanate compounds, melamine resins, urea resins, and polyol compounds. Among these, isocyanate compounds are particularly preferred. The ferromagnetic particles used in the present invention include γ-Fe ₂ O ₃ having a spinel structure, CrO ₂ , cobalt ferrite (CoO Fe ₂ O ₃ ), cobalt-adsorbed iron oxide, and ferromagnetic Fe-Co-Ni. Examples include alloys. The magnetic recording medium of the present invention may optionally contain plasticizers such as dibutyl phthalate and triphenyl phosphate, dioctyl sulfonate sodium succinate, t-butylphenol-polyethylene ether, ethylnaphthalene-sodium sulfonate,
Lubricants and various antistatic agents can also be added, such as dilauryl succinate, zinc stearate, soybean oil lecithin, silicone oil. Hereinafter, the present invention will be specifically explained with reference to Examples. In the examples, parts simply indicate parts by weight. The reduced viscosity η sp/c (dl/g) was measured at 30°C by dissolving 0.10 g of polyester resin or polyurethane resin in 25 ml of phenol/tetrachloroethane (6/4). Production example of polyester resin In an autoclave equipped with a thermometer and a stirrer, 776 parts of dimethyl terephthalate, 388 parts of dimethyl isophthalate, 360 parts of the above phosphorus compound (0), 818 parts of ethylene glycol, 915 parts of neopentyl glycol, and tetrabutoxy Charge 1.7 parts of titanate and heat at 150 to 230°C for 120 minutes to perform transesterification, then charge 438 parts of adipic acid and heat to 220 to 230
The reaction was further carried out at 230°C for 1 hour. Next, the temperature of the reaction system was raised to 270° C. over 30 minutes, and the pressure of the system was gradually reduced to 0.1 to 0.2 mmHg after 45 minutes, and the reaction was continued under these conditions for an additional 60 minutes. The reduced viscosity of the obtained polyester resin A is
0.58, and the phosphorus content was 1.3%. Polyester resin B shown in Table 1 was prepared using the same manufacturing method.
~E was obtained. The resin composition was analyzed using NMR. Polyester resin F in Table 1 was gelled. The structural unit of polyester resin F represents the molar ratio of acid component and glycol component at the time of charging raw materials.

[Table] Example of manufacturing polyurethane resin 109 parts of toluene and 109 parts of methyl ethyl ketone were placed in a reaction vessel equipped with a thermometer, stirrer, and reflux condenser.
part, has the same composition as polyester resin A, but
100 parts of polyester resin A' with a molecular weight of 2000, 10 parts of neopentyl glycol, 35 parts of diphenylmethane diisocyanate, and dibutyltin dilaurate.
0.05 part was charged and reacted at 70 to 80°C for 6 hours. The polyurethane resin obtained by evaporating the solvent from the reaction solution had a reduced viscosity of 0.75 and a phosphorus content of 0.88%. Polyurethane resins shown in Table 2 were obtained. Polyurethane resin ~ was obtained in the same manner.

【table】

[Table] Examples 1 to 7, Comparative Examples 1 to 5 Magnetic powder (cobalt-coated γ-Fe ₂ O ₃ ) 60 parts Polyester resin A solution (solid content 30%, solvent methyl ethyl ketone/toluene = 1/1 part by weight )
50 parts Isocyanate compound (Desmodyur L,
Bayer) 2 parts Methyl ethyl ketone 50 parts Toluene 50 parts Methyl isobutyl ketone 25 parts After mixing the above composition in a ball mill for 24 hours,
This magnetic paint was applied to a thickness of 6 μm on a 25 μm polyethylene terephthalate film, and then applied for 0.05 seconds.
The film was subjected to magnetic field orientation treatment in the longitudinal direction using a DC magnetic field of 2500 Gauss, and after drying with hot air at 100° C. for 1 minute, calendering treatment was performed. The Br/Bm value of the obtained tape was 0.85. Next, commercially available cellophane tape was attached to the surface of the magnetic coating, and then the cellophane tape was peeled off, but the magnetic coating did not peel off from the polyester film and the adhesion was good. Methyl ethyl ketone of polyester resin or polyurethane resin shown in Table 1 and Table 2
A magnetizable layer was formed on a polyethylene terephthalate film in a similar manner using a 30% solution of toluene (1/1 weight ratio). Table 3 shows the measurement results for each magnetizable layer.

[Table] As is clear from Table 3, when the polyurethane resin or polyurethane resin of the present invention is used, a magnetic recording medium with increased magnetic susceptibility (Br/Bm) and excellent adhesion and smoothness can be obtained. .

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, in which a phosphorus compound having an ester-forming functional group is used as the binder. A magnetic recording medium characterized by using a reacted polyester resin and/or polyurethane resin. 2. The magnetic recording medium according to claim 1, wherein the phosphorus compound having an ester-forming functional group is a phosphorus compound represented by the following formula (). (In the formula, R ₁ is a monovalent ester-forming functional group. _{R 2} and R ₃ are the same or different groups,
It is selected from the group consisting of a monovalent hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, and a monovalent ester-forming functional group. A represents a divalent or trivalent organic residue. Further, n ₁ is 1 or 2, and n ₂ and n ₃ are each an integer of 0 to 4. ) 3 A patent claim characterized in that it is a polyester resin and/or polyurethane resin in which a phosphorus compound having an ester-forming functional group is reacted so that the phosphorus content in the entire resin is 500 to 40,000 ppm. The magnetic recording medium according to scope 1.